Nanoporous spongelike Au–Ag films for electrochemical epinephrine sensing

• Nanoporous spongelike Au–Ag electrode was fabricated via electrodeposition followed by selective etching.
• The electrochemical properties of the electrode were investigated.
• Electrode has excellent catalytic activity for oxidation of epinephrine.
• Epinephrine was determined by LSV, DPV and chronoamperometry.

A simple strategy to fabricate an efficient electrochemical sensor for epinephrine (EP) oxidation is developed by selective etching of the electrodeposited thin Au–Ag alloyed film. The electrochemical characterization of obtained nanoporous spongelike Au–Ag electrodes was carried out by cyclic voltammetry (CV) and chronoamperometry. It was found that the nanoporous Au-Ag electrode exhibits a significantly higher electrocatalytic activity toward EP oxidation when comparing with a bulk Au electrode. The performed electrochemical tests demonstrated that EP oxidation and reduction processes are controlled by diffusion. The transfer coefficient (α = 0.55) and total number of electrons involved in the anodic oxidation of epinephrine to adrenalinequinone (n = 2) as well as the diffusion coefficient of EP in the 0.1 M phosphate buffer solution PBS (D = 1.29 × 10− 5 cm2 s− 1) were evaluated. Using chronoamperometry, the average catalytic rate constant was calculated to be 2.16 × 105 M− 1 s− 1. Under the optimized conditions, the electrochemical sensor exhibited a linear response for EP concentration over the range of 25–300 μM for linear sweep voltammetry (LSV), 10–100 μM for differential pulse voltammetry (DPV) and 25–700 μM for chronoamperometry. The DPV method has the highest sensitivity (1.52 mA cm− 2 mM− 1) and the lowest detection limit (5.05 × 10− 6 M).

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